There have been thin-film solar cells including a light absorbing layer using CuInSe2 being a compound-semiconductor thin film of a chalcopyrite structure composed of a Group-Ib, a Group-IIIb, and a Group-VIb element (that is a CIS-based thin film), or Cu(In, Ga)Se2 being a solid solution thereof with Ga as a solute (that is a CIGS-based thin film). They have been adapted for high efficiencies of energy conversion with reduced deteriorations of efficiency such as due to light irradiation, as an advantage.
For CIS-based thin films being a compound-semiconductor thin film of chalcopyrite structure, or for CIGS-based thin films being a solid solution thereof with Ga as a solute, typically implemented has been a film formation at 5500 C in view of a film quality not to be deteriorated and leak currents not to be increased. It has been considered that at lower temperatures than 5500 C the formation would produce smaller particle diameters, degrading dark current characteristics. It is noted that semiconductor integrated circuits have heat resistant limits about 4000 C.
There have been literatures (cf. e.g. Patent Literature 1) disclosing solid-state imaging devices including thin film transistors as switching elements formed on a substrate, and an amorphous semiconductor layer as a sensor region laminated thereon, with interposed pixel electrodes connected to the switching elements, as well as solid-state imaging devices having the above-noted substrate made up by an insulating substrate.
According to the Patent Literature 1, those solid-state imaging devices have the amorphous semiconductor layer employed as a photo sensor region, rendering target wavelengths of photoelectric conversion mostly within a visible wavelength band.    Patent Literature 1: Japanese patent Application Laying-Open Publication No 2001-144279